I am wondering if it is possible in C to overwrite the contents of one array with another, and by doing so, how do I work around with the loss of array size?
Say I have two arrays.
int a[] = {1,2,3,4,6,7,8};
int b[] = {1,6};
// How can I overwrite the array a with array b, so get the following?:
a[] = {1,6};
When you declare an array like a[] = {...} the array gets a fixed size which cannot be altered, the size is determined when you compile.
If you want to use dynamic arrays you need to allocate on the heap, in C this is done with malloc and realloc. realloc allows you to resize an array.
e.g.
char* p = malloc(10);
char* q = realloc(p, 5); // now you made the array 5 bytes shorter
you should check the return value of realloc in order to know whether the realloc was successful.
char* q = realloc(p, 5);
if (q != NULL) // successful
You cannot do that, like @Klutt & @david-ranieri said in comments you can copy the content of b in a and then fill with 0.
But I recommend to use dynamic array, since C++11 you can do :
// initialise with braced-init-list
int* a = new double[8] { 1, 2, 3, 4, 5, 6, 7, 8};
int* b = new double[2] { 1, 6};
delete[] a;
a = b;
8 * sizeof(int) you cannot transform it to an array of size 2 * sizeof(int), but if you use pointers (heap) you only point to the beginning of the allocated area so you can tell the memory that now a point to the beginning of the area pointed by b
memcpy(a, b, sizeof(b)); memset(a + (sizeof(b) / sizeof(b[0])), 0, sizeof(a) - sizeof(b));